In March, 2005, the United States became the first nation to regulate mercury (Hg) emissions from coal-fired power plants. At that time, the Environmental Protection Agency (EPA) issued its Clean Air Mercury Rule (CAMR), which affects all utilities nationwide, and which has, as its objective, the reduction of utilities' Hg discharges from the then-current level of 48 ton/yr to 15 ton/yr by 2018, about a 70% reduction. Mandatory emission caps, declining with time, are coupled with severe penalties for noncompliance. Clearly, coal-fired power plants, and all other facilities which discharge gaseous emissions containing mercury, have incentives, financial and otherwise, to implement new and low-cost ways to reduce Hg emissions and improve the effectiveness of their pollution control equipment.
Conventional methods for removing particulates from gas streams have included various configurations of filter elements, some of which are self-supporting and some of which are mounted within suitable support structures. Such filter elements include filter bags, filter tubes, filter cartridges, canisters, and flat panels. These various filtration components are typically supported and housed in an installation termed a “baghouse”.
Additionally, activated carbon (AC) powders have been used for the capture of mercury and other contaminants from flue gas streams from power plants, incinerators, crematoria and other, similar, mercury-containing discharges. For example, commonly assigned U.S. patent application Ser. No. 10/272,487, filed Oct. 16, 2002, discloses a filtration system uniquely suited for the capture of mercury from flue gases. That system, which is incorporated here by reference, includes a filter element and an adsorbent component having a mercury-capturing component positioned on the downstream side of the filter element.
U.S. Pat. No. 6,322,613B1 discloses a process for recovering mercury from a gaseous mixture in which a carbonaceous feed stock, in particular scrap tires and rubber waste, is first pyrolyzed and activated to produce an activated carbon sorbent having a sulfur content of at least 3 weight percent (col. 1, lines 60-65), and then a gas stream containing mercury is passed over this sorbent at a low temperature, e.g. 50-200° C., thereby producing a mercury-containing sorbent and a stripped gas stream. This is followed by passing a regenerating gas stream over the sorbent, at a higher temperature, to produce a mercury-rich gas stream and to regenerate the sorbent (col. 2, lines 1-8).
In addition, the patent literature and the general technical literature are replete with references disclosing elemental sulfur in use in various processes for stripping mercury from flowing gas streams, including from combustion flue gases.
None of this known, voluminous art, however, discloses or suggests a composition and a process, useful in the capture of mercury from a gaseous mixture containing SO2 and NOx and mercury, which have a mercury capture capacity from such gaseous mixtures exceeding 10 mg Hg per gram of adsorbent. Indeed, a mercury capture capacity from such gaseous mixtures exceeding 100 mg Hg per gram adsorbent is made possible by the instant invention, providing an advantageous composition for use in meeting the aforesaid EPA regulations.